Modulation and coding for multiple resource units in wireless network

ABSTRACT

Methods and devices for transmitting data in an Orthogonal Frequency-Division Multiple Access (OFDMA) wireless local area network, comprising: selecting, for a first resource unit assigned to the target station, a first modulation type; selecting, for a second resource unit assigned to the target station, a second modulation type different from the first modulation type; and modulating coded data and mapping the modulated data onto subcarriers associated with the assigned resource units based on the respective modulation types selected for each of the assigned resource units.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application is a continuation of U.S. patent applicationSer. No. 17/145,199 filed Jan. 8, 2021, entitled “MODULATION AND CODINGFOR MULTIPLE RESOURCE UNITS IN WIRELESS NETWORK” and claims the benefitof and priority to U.S. Provisional Patent Application No. 62/959,603filed Jan. 10, 2020, entitled “MODULATION AND CODING FOR MULTIPLERESOURCE UNITS IN WIRELESS NETWORK”, the contents of which areincorporated herein by reference.

TECHNICAL FIELD

The present application relates to mobile air interface technologies, inparticular to methods and systems for modulating and coding data fortransmission in a wireless network.

BACKGROUND

Networks that operate according to Wi-Fi protocols, including IEEE802.11 protocols such as the IEEE 802.11ax specified in IEEE DraftP802.11ax_D6.0, use defined modulation and coding schemes (MCSs) thatspecify properties used for physical layer modulation and encoding.

A new protocol, IEEE 802.11be, is currently under development by IEEE802.11 Task Group TGbe, and will be the next major IEEE 802.11 amendmentto define the next generation of Wi-Fi after IEEE 802.11ax (currentlyIEEE Draft P802.11ax_D6.0). IEEE 802.11be (also called Extremely HighThroughput (EHT)) is expected to support a data rate of at least 30 Gbpsand may use a spectrum bandwidth up to 320 MHz for unlicensedoperations, double the 160 MHz maximum bandwidth currently contemplatedby IEEE 802.11ax.

IEEE 802.11ax supports Orthogonal Frequency-Division Multiple Access(OFDMA) transmission, in which data intended for different stations canbe multiplexed within an OFDM symbol through the allocation of differentsubsets of subcarriers (tones). In IEEE 802.11ax, a Resource Unit (RU)includes a group of contiguous subcarriers defined in the frequencydomain. Different RUs can be assigned to different stations within a PHYprotocol data unit (PPDU). Each RU is used for one OFDM symbol for onestation (also referred to as a STA). FIG. 1 illustrates an example ofstation (STA) resource allocation in IEEE 802.11ax. In the allocated RU,the MCS for each station is the same across all the OFDM symbols (i.e.,a single MCS is used for each station) within one PPDU. The MCSs usedfor RUs for different stations can be different within one PPDU.

In IEEE 802.11ax, RUs are defined based on RU sizes such as 26-tone RU,52-tone RU, 106-tone RU, 242-tone RU, 484-tone RU, 996-tone RU and2×996-tone RU. Information about the RU assigned to a station, such asthe RU location and the RU size, and the modulation and coding scheme(MCS) for the data transmitted over the assigned RU, are indicated inthe HE-SIG-B field of the physical layer (PHY) protocol data unit (PPDU)in IEEE 802.11ax. The MCS information is provided in the form of an MCSindex that specifies a set of physical layer properties includingmodulation and forward error correction (FEC) coding rate R. By way ofillustrative example, FIG. 2 illustrates the examples of MCSs specifiedin IEEE 802.11ax for the case of a 26-tone RU where the number ofspatial streams Nss=6.

Under IEEE 802.11ax, the MCS used for an RU is determined based on thechannel conditions for the data transmission. In particular, channelconditions are measured and averaged over all resources assigned for astation, and the average result used to select an appropriate MCS.

As indicated above, IEEE 802.11be will support a wide bandwidth, up to320 MHz. The larger bandwidth introduces opportunities and issues thatare not present in a narrower bandwidth system. For example, EHT enabledWi-Fi should enable a significant growth in the volume of highthroughput data transmission as well as a proliferation of an extremelylarge number of low data rate devices such as Internet of Things (IoT)devices. However, as a result of the anticipated deployment density, theprobability of a single station having access to a large number ofcontiguous subcarriers within the 320 MHz bandwidth at any given timecan be expected to be low. In this regard, an operating feature calledmultiple RUs (multi-RU) has been proposed for IEEE 802.11be, in whichmultiple RUs that each have a respective sub-set of contiguoussubcarriers can be allocated for one station in an OFDM symbol.

Channel conditions for an OFDM symbol may have greater variance across awide bandwidth than for a narrow bandwidth. For example, it is highlypossible that the interference levels for subsets of subcarriers may besignificantly different across the whole bandwidth, especially forsubcarriers that are separated far apart in frequency domain.

Accordingly, there is a need for further development of modulation andcoding schemes that can be applied to optimize channel efficiency inlarge bandwidth multi-RU applications.

SUMMARY

According to a first example aspect is a method of transmitting data inan Orthogonal Frequency-Division Multiple Access (OFDMA) wireless localarea network. The method includes selecting, for a first resource unitassigned to the target station, a first modulation type; selecting, fora second resource unit assigned to the target station, a secondmodulation type different from the first modulation type; and modulatingcoded data and mapping the modulated data onto subcarriers associatedwith the assigned resource units based on the respective modulationtypes selected for each of the assigned resource units.

In some examples, such a method can enable different modulation types tobe used for different sets of sub-carriers assigned to a single targetstation, thereby allowing differences in channel conditions between thetwo sets of subcarriers to be addressed without resorting to the lowestcommon denominator. This can enable more efficient use of computationalresources at a transmit station and target station and more efficientuse of network resources within the WLAN network.

In some examples, the method includes selecting, for each of the firstresource unit and second resource unit assigned to the target station, arespective code rate, and prior to modulating the data, encoding thedata based on the respective code rates selected for each of the firstand second resource units.

In some examples, the method includes determining link conditions forthe subcarriers associated with each of the first and second resourceunits, wherein the selecting the respective modulation types is based onthe link conditions. In some examples, selecting the respective coderates is based on the link conditions.

In some examples, the method includes putting information about therespective modulation types selected for the resource units in a headerof the data unit.

In some examples, the method includes putting information about therespective code rates selected for the resource units in a header of thedata unit.

According to a second example aspect is a method of transmitting a dataunit in a wireless local area network, the data unit comprising aphysical payload that includes an Orthogonal Frequency-DivisionMultiplexing (OFDM) symbol that comprises a plurality of resource unitsused for data modulated according to a respective modulation type,wherein the resource units include first and second resource unitsintended for a same receiving station and further resource unitsintended for one or more further receiving stations, the data unitcomprising a header that includes, individually for each of the firstand second resource unit, information identifying the respectivemodulation types used to modulate the data of the first and secondresource units, respectively.

According to a third example aspect is a method of receiving a data unitin wireless local area network, the data unit comprising a physicalpayload that includes an Orthogonal Frequency-Division Multiplexing(OFDM) symbol that comprises a plurality of resource units used for datamodulated according to a respective modulation type, wherein theresource units include a first and second resource unit intended for asame receiving station and further resource units intended for one ormore further receiving stations, the data unit comprising a header thatincludes, individually for each of the first and second resource units,information identifying the respective modulation types used to modulatethe data of the first and second resource units, respectively.

In some examples of the second and third example aspects, the headerincludes individual subfields for each of the first and second resourceunits for the information identifying the respective modulation typedused to modulate the data of the first and second resource units. Insome examples, the header also includes, individually for each of thefirst and second resource units, information identifying a respectivecode rate used to encode the data carried by the first and secondresource units, wherein the information identifying the modulation typeand the information identifying the code rate are specified by amodulation and coding scheme (MCS).

According to a fourth example aspect is a method of transmitting data inan Orthogonal Frequency-Division Multiple Access (OFDMA) wireless localarea network (WLAN), comprising: selecting, for a first resource unitassigned to a target station, a first modulation type; selecting, for asecond resource unit assigned to the target station, a second modulationtype different from the first modulation type; parsing input data forthe target station into a first data stream and a second data stream;modulating, using the first modulation type, data included in the firstdata stream and mapping the modulated data onto a first set ofsubcarriers associated with the first resource unit; modulating, usingthe second modulation type, data included in the second data stream andmapping the modulated data onto a second set of subcarriers associatedwith the second resource unit; and transmitting, in the WLAN, anorthogonal frequency division multiplexing (OFDM) symbol including thedata modulated onto the first set of subcarriers and the data modulatedonto the second set of subcarriers.

In some examples of the fourth example aspect, the first set ofsubcarriers is separated in frequency from the second set of subcarriersby a plurality of intervening subcarriers.

In some examples of the fourth example aspect, the method includesdetermining link conditions in the WLAN for the first set of subcarriersand the second set of subcarriers, wherein the first modulation type isselected based on the link conditions for the first set of subcarriersand the second modulation type is selected based on the link conditionsfor the second set of subcarriers.

In some examples of the fourth example aspect, the method comprises,prior to parsing the input data for modulating, encoding the dataaccording to a first code rate.

In some examples of the fourth example aspect, the method comprisesselecting, for a first code rate for the first resource unit and asecond code rate for the second resource unit; prior to modulating thedata included in the first data stream, encoding the data included inthe first data stream based on the first code rate; and prior tomodulating the data included in the second data stream, encoding thedata included in the second data stream based on the second code rate.In some examples, the method comprises determining link conditions inthe WLAN for the first set of subcarriers and the second set ofsubcarriers, wherein the first modulation type and first code rate areselected based on the link conditions for the first set of subcarriersand the second modulation type and second code rate are selected basedon the link conditions for the second set of subcarriers.

In some examples of the fourth example aspect, the first modulation typeand the second modulation type are each selected from a group ofmodulation types that includes: binary phase shift keying (BPSK)modulation, quadrature phase shift keying (QPSK) modulation;16-quadrature amplitude modulation (QAM); 64-QAM; 256-QAM; 1024-QAM;2048-QAM; and 4096-QAM.

In some examples of the fourth example aspect, the OFDM symbol istransmitted as part of a data unit that includes information indicatingthe first modulation type, the first code rate, the second modulationtype and the second code rate in a preamble header of the data unit.

In some examples of the fourth example aspect, the OFDM symbol istransmitted as part of a physical payload of a data unit, the data unitcomprising a header that includes, individually for each of the firstand second resource unit, information identifying the first set ofsubcarriers, the first modulation type, the second set of subcarriersand the second modulation type. In some examples, the header includesindividual subfields for information identifying the first modulationtype and the second modulation type.

According to a fifth example embodiment is a transmit station fortransmitting data in an Orthogonal Frequency-Division Multiple Access(OFDMA) wireless local area network (WLAN), comprising: a networkinterface configured to send and receive signals in the WLAN; aprocessing device coupled to the network interface; a non-transitorystorage coupled to the processing device and storing thereoninstructions that, when executed by the processing device, configure thetransmit station to: select, for a first resource unit assigned to atarget station, a first modulation type; select, for a second resourceunit assigned to the target station, a second modulation type differentfrom the first modulation type; parse input data for the target stationinto a first data stream and a second data stream; modulate, using thefirst modulation type, data included in the first data stream andmapping the modulated data onto a first set of subcarriers associatedwith the first resource unit; modulate, using the second modulationtype, data included in the second data stream and mapping the modulateddata onto a second set of subcarriers associated with the secondresource unit; and transmit, in the WLAN, an orthogonal frequencydivision multiplexing (OFDM) symbol including the data modulated ontothe first set of subcarriers and the data modulated onto the second setof subcarriers.

According to a sixth example aspect is a method comprising:

receiving, at a receiving station, a data unit transmitted in wirelesslocal area network (WLAN), the data unit comprising a physical payloadthat includes an Orthogonal Frequency-Division Multiplexing (OFDM)symbol that has been transmitted in a plurality of resource units usedfor data modulated according to a respective modulation type, whereinthe resource units include a first and second resource unit assigned tothe receiving station and further resource units assigned to one or morefurther receiving stations, the data unit comprising a header thatincludes, individually for each of the first and second resource units,information identifying the respective modulation types used to modulatethe data transmitted in the first and second resource units,respectively. According to further example aspects is a non-transitorycomputer readable storage that stores instructions that when executed bya processor device of a station can configure the station to perform anyof the methods of the preceding aspects.

According to a seventh aspect is a method of transmitting data in anOrthogonal Frequency-Division Multiple Access (OFDMA) wireless localarea network (WLAN), including: parsing input data for transmission fora receiving station into a first data stream and a second data stream;modulating, using a first modulation type, data included in the firstdata stream and mapping the modulated data onto a first set ofsubcarriers associated with a first resource unit; modulating, using asecond modulation type, data included in the second data stream andmapping the modulated data onto a second set of subcarriers associatedwith a second resource unit; and transmitting, in the WLAN, anorthogonal frequency division multiplexing (OFDM) symbol including thedata modulated onto the first set of subcarriers and the data modulatedonto the second set of subcarriers.

According to an eighth aspect is a station for transmitting data in anOrthogonal Frequency-Division Multiple Access (OFDMA) wireless localarea network (WLAN), including: a network interface configured to sendand receive signals in the WLAN; a processing device coupled to thenetwork interface; a non-transitory storage coupled to the processingdevice and storing thereon instructions that, when executed by theprocessing device, configure the station to: parse input data for areceiving station into a first data stream and a second data stream;modulate, using a first modulation type, data included in the first datastream and map the modulated data onto a first set of subcarriersassociated with a first resource unit; modulate, using a secondmodulation type, data included in the second data stream and map themodulated data onto a second set of subcarriers associated with a secondresource unit; and transmit, in the WLAN, an orthogonal frequencydivision multiplexing (OFDM) symbol including the data modulated ontothe first set of subcarriers and the data modulated onto the second setof subcarriers.

According to a ninth aspect is a method that includes: receiving, at areceiving station, a data unit transmitted in wireless local areanetwork (WLAN), the data unit comprising a physical payload thatincludes an Orthogonal Frequency-Division Multiplexing (OFDM) symbolthat has been transmitted in a plurality of resource units used for datamodulated according to a respective modulation type, wherein theresource units include a first and second resource unit assigned to thereceiving station and further resource units assigned to one or morefurther receiving stations, the data unit comprising a header thatincludes, for each of the first and second resource units, informationidentifying the respective modulation types used to modulate the datatransmitted in the first and second resource units, respectively.

According to further example aspects is a station enabled for use in awireless area local area network (WLAN), the station being configured toperform one or more of the above methods.

BRIEF DESCRIPTION OF THE DRAWINGS

Reference will now be made, by way of example, to the accompanyingfigures which show example embodiments of the present application, andin which:

FIG. 1 illustrates an example of station (STA) resource allocation in802.11ax.

FIG. 2 illustrates the examples of MCSs specified in IEEE 802.11ax forthe case of a 26-tone RU where the number of spatial streams Nss=6.

FIG. 3 shows an example of multiple RUs allocated to one stationaccording to an example embodiment.

FIG. 4 is a block diagram illustrating an example communication networkin accordance with one implementation of the present disclosure;

FIG. 5 is a block diagram illustrating components of a transmitter inaccordance with one implementation of the present disclosure;

FIG. 6 illustrates example frame format for exchanging informationthrough a wireless medium of the communication network of FIG. 4;

FIG. 7 is a block diagram illustrating components of a transmitter inaccordance with a further implementation of the present disclosure;

FIG. 8 is a block diagram illustrating components of a receiver inaccordance with an implementation of the present disclosure;

FIG. 9 is a block diagram illustrating components of a receiver inaccordance with a further implementation of the present disclosure;

FIG. 10 is a block diagram illustrating a processing system which may beused in one or more stations of the communication network of FIG. 4according to example embodiments.

Like reference numerals are used throughout the Figures to denotesimilar elements and features. While aspects of the invention will bedescribed in conjunction with the illustrated embodiments, it will beunderstood that it is not intended to limit the invention to suchembodiments.

DETAILED DESCRIPTION OF EXAMPLE EMBODIMENTS

The present disclosure teaches methods, devices, and systems fortransmitting data in a wireless network. Next generation wireless localarea network (WLAN) systems, including for example next generation Wi-Fisystems such as the EHT system proposed under the developing IEEE802.11be protocol, will have access to larger bandwidth. As noted above,a multi-RU feature has been proposed for IEEE 802.11be to allow multipleRUs to be allocated for one station in an OFDM symbol. However, existingproposals for multi-RU do not account for variations in link or channelconditions that may occur across the respective subcarrier groupsallocated to the multiple RUs assigned to a particular station. Asindicated above, under IEEE 802.11ax the MCS used for an RU isdetermined based on the link conditions for the data transmission. Inparticular, link conditions are measured and averaged over all resourcesassigned for a station, and the average result used to select anappropriate MCS. However, the use of a single MCS for all RUs assignedto a single station may be an inefficient solution in the context ofmulti-RU in which the different RUs assigned to a station may userespective sets of subcarriers that are spaced relatively far apart infrequency. Assuming that a single MCS applies to all RUs in themulti-RU, even if one single RU has a relatively lowersignal-to-interference-plus-noise ratio (SINR) value and another RU hasrelatively larger SINR value(s), a transmitting station will selecteither an MCS that is suitable for the worst RU with the lowest SINR oran MCS that is lower than the MCS which is good for the best RU(s). Animproved solution is to apply a flexible MCS selection, such thatdifferent RUs can have different MCS.

Accordingly, in example embodiments, in the case where multiple RUs areassigned to a single target station, MCS selection is performedindependently for each of the multiple RUs. In example embodiments, MCSselection for each RU assigned to a station is based on the link orchannel conditions for the subcarriers assigned to that particular RU.

In this regard, FIG. 3 illustrates a representative example of multipleRUs assigned to a single station (STA 0) according to exampleembodiments. In the example of FIG. 3, the STA (STA 00) has beenassigned two non-contiguous RUs, namely RU 0 and RU 2, in each of aplurality of OFDM symbols Sym 0 to Sym N−1 within a PPDU. A first MCS,namely MCS(i), is used for modulating and encoding data that istransmitted using the first RU 0, and a second MCS, namely MCS(j), isused to for modulating and encoding data that is transmitted using thesecond RU 2. In example embodiments, MCS(i) is selected for the first RU0 based on the link conditions measured in respect of the set ofsubcarriers associated with RU 0, and MCS(j) is selected for the secondRU 2 based on wireless channel conditions measured in respect of the setof subcarriers associated with RU 2.

The MCS selected for an RU specifies a defined set of properties usedfor physical layer encoding and modulating of data that is used for theRU. For example, for an RU having a specified number of tones (e.g. RUsize=26, 52, 106, 242, 484, 996 tones), the MCS selected for that RUwill specify the modulation type (e.g., binary phase shift keying(BPSK), quadrature phase shift keying (QPSK), 16-quadrature amplitudemodulation (QAM), 64-QAM, 256-QAM, 1024-QAM, 2048-QAM, and 4096-QAM) andthe forward error correction (FEC) coding rate (e.g., ½, ⅔, ¾, ⅚) thatis used for the RU included in a PPDU. Examples of types of otherproperties that may be specified by the MCS are represented in theillustrative table of FIG. 2.

An example of an environment in which MCS selection can occur isillustrated in FIG. 4. FIG. 4 illustrates a communication network 100comprising a plurality of stations (STAs) that can include fixed,portable, and moving stations. The example of FIG. 1 illustrates asingle fixed STA, access-point station (AP-STA) 104, and a plurality ofSTAs 102 that may be portable or mobile. The network 100 may operateaccording to one or more communications or data standards ortechnologies, however in at least some examples the network 100 is aWLAN, and in at least some examples is a next generation Wi-Fi compliantnetwork that operates in accordance with one or more protocols from the802.11 family of protocols.

Each STA 102 may be a laptop, a desktop PC, PDA, Wi-Fi phone, wirelesstransmit/receive unit (WTRU), mobile station (MS), mobile terminal,smartphone, mobile telephone, sensor, internet of things (IOT) device,or other wireless enabled computing or mobile device. In someembodiments, a STA 102 comprises a machine which has the capability tosend, receive, or send and receive data in the communications network100 but which performs primary functions other than communications. TheAP-STA 104 may comprise a network access interface which functions as awireless transmission and/or reception point for STAs 102 in the network100. The AP-STA 104 may be connected to a backhaul network 110 whichenables data to be exchanged between the AP-STA 104 and other remotenetworks (including for example the Internet), nodes, APs, and devices(not shown). The AP-STA 104 may support communications throughunlicensed radio frequency spectrum wireless medium 106 with each STA102 by establishing uplink and downlink communication links or channelswith each STA 102, as represented by the arrows in FIG. 1. In someexamples, STAs 102 may be configured to communicate with each other.Communications in the network 100 may be unscheduled, scheduled by theAP-STA 104 or by a scheduling or management entity (not shown) in thenetwork 100, or a mix of scheduled and unscheduled communications.

FIG. 5 illustrates an example of selected components of a transmitter118 that may be present in a STA, for example AP-STA 104 according toexample embodiments. In example embodiments, RUs have been allocated touse for data transmission among the multiple STAs 102, and multiplenon-contiguous RUs (e.g., RUi and RUj) have been assigned to the sameSTA 102. In example embodiments, the AP-STA 104 acquires informationabout link conditions through the wireless medium 106 for the RUsassigned to STAs 102. Based on that information, the AP-STA 104 selectsan optimal MCS for each RU from a predefined set of available MCSs. Inan example embodiment, the link conditions for RUi and RUj aredetermined to be sufficiently different that a different optimal MCS(e.g. MCS(i) and MCS(j) is selected for RUi and RUj.

The transmitter 118 receives a serial stream of data bits as input 120.In example embodiments, the input 120 includes data bits that are to beincluded in the physical layer (PHY) payload (e.g., the PHY service dataunit (PSDU) of a multi-RU physical layer (PHY) protocol data unit(PPDU)). An encoder parser 122 of the transmitter 118 parses the inputdata bits into N parallel data streams S1 to SN, each of whichcorresponds to a respective RU 1 to RU N. In example embodiment, atleast two of the streams (e.g. Si and Sj) include data that is intendedfor the same receiving STA 102. FEC coding is applied to each of thedata bit streams S1 to SN by respective FEC encoders 124(1) to 124(N).In example embodiments, data streams S1 to SN are each segmented intosource words that are respectively FEC encoded into respective codewords C1 to CN. The coding rate (e.g., ½, ⅔, ¾, ⅚) that is applied ateach encoder 124(1) to 124(N) is determined by the MCS selected for thecorresponding RU 1 to RU N. Accordingly, the code rate applied to thesource words included in data streams Si and Sj are determined by thecoding rates specified by MCS(i) and MCS(j), respectively, resulting inrespective codewords Ci and Cj. Each of the code words C1 to CN is thenmodulated at a respective modulator 126(1) to 126(N) and mapped onto arespective set of subcarriers. Each set of subcarriers corresponds to arespective RU, i.e., RU 1 to RU N. In particular, code words C1 to CNare each mapped to respective sets of subcarriers or tones thatcorrespond to RU 1 to RU N using a respective modulation constellation(e.g., BPSK, QPSK, 16-QAM, 64-QAM, 256-QAM, 1024-QAM, 2048-QAM,4096-QAM). The modulation type applied at each of the respectivemodulators 126(1) to 126(N) is determined by the MCS selected for thecorresponding RU 1 to RU N. Accordingly, the modulation applied to thecode words Ci and Cj are determined by the modulation constellationsspecified by MCS(i) and MCS(j), respectively, resulting in respectiveresource units RU i and RU j.

In example embodiments, further processing operations 128 are applied toRU 1 to RU N to generate output 130. In example embodiments furtherprocessing operations 128 include an inverse fast Fourier transform(IFFT) operation on each of the subcarriers, followed by a parallel toserial (p/s) conversion and the addition of a guard interval (GI). Theresulting output is a stream of OFDM symbols for inclusion in a PHYpayload (e.g., PSDU) of a PPDU.

In example embodiments, the output 130, which corresponds to the dataportion (e.g., PHY payload) of a PPDU, is appended to a PHY header toprovide a PPDU that is modulated onto a carrier frequency andtransmitted through wireless medium 106. In this regard, FIG. 6illustrates an example frame format that may be used for an EHT PPDUaccording to example embodiments. As illustrated, the PHY headerappended to the data portion (e.g., PHY payload) of a PPDU may includethe following header fields: EHT preamble, U-SIG and EHT-SIG. In exampleembodiments, information about the RUs assigned to a STA, such as the RUlocation and the RU size, and the MCS selected for the data transmittedover the assigned RU, can be indicated in the EHT-SIG field of the PPDU.For example, the EHT-SIG field may include subfields for each STA 102(e.g. User field 1 to User field M). Each user field can includesubfields that specify: STA-ID that uniquely identifies the target STA,the RUs assigned to the target STA, and the MCSs used for each of therespective RUs assigned to the target STA (e.g., MCS(i) for RU i; MCS(j)for RU j).

In example embodiments, the MCS subfields can be populated with an MCSindex value that maps to the specified MCS applied to the RU. Forexample, MCS values similar to the 4-bit MCS index values specified inIEEE 802.11ax can be used. In the case of IEEE 802.11ax, the 4-bit MCSindex values each map to a respective set of MCS properties that specifyboth a coding rate and a modulation type.

In the example embodiment of FIG. 5, each RU in a multi-RU for a STA canuse an independent code rate and modulation type. This embodiment mayoptimize the overall multi-RU performance by optimizing the performanceof each RU. A large number of optimization options are made availablethrough the application of MCSs to individual RUs based on the channelor link conditions specific to each RU.

In the case of a further example embodiment that will be describedbelow, a common encoder can be used for all RUs for a specific targetSTA. In such cases, a common MCS field can be included in the header toindicate a base MCS for all RUs. The base MCS field will indicate thecommon code rate for all the RUs for a specific target STA. The headerwill further include RU specific MCS index subfields to indicate themodulation order or type for that specific RU. In this regard, the RUspecific MCS index subfields may in some examples be shorter becauserather than indicating an entire MCS option, the subfield need onlyidentify one of the different possible modulation orders or types thatcan be used with the specified code rate (e.g., BPSK, QPSK, 16-QAM,64-QAM, 256-QAM, 1024-QAM, 2048-QAM, 4096 QAM). For example, rather thanrequiring a 4-bit MCS index value in the subfield for each RU, the MCSindex value for each RU can be shorter, for example 3 bits or fewer toindicate a difference in a modulation type relative to a base MCS thatmay be specified at another location in the header by a common 4-bitindex for all RUs.

In this regard, FIG. 7 illustrates an example of selected components ofa further transmitter 140 that may be present in a STA, for exampleAP-STA 104 according to example embodiments. In example embodiments,transmitter 140 is identical in operation to transmitter 118 describedabove with the exception that transmitter 140 applies common FECencoding with the same code rate to all RUs included in a PPDU. In theexample of transmitter 140, the base MCS including the code rate may beselected based on the link condition across the entire ODFM symbolbandwidth, but the modulation type is selected based on the linkcondition for the bandwidth associated with each of the respective RUs.

In this regard, the transmitter 140 receives a serial stream of databits as input 120 that are to be included in a PSDU of a multi-RU PPDU.Before parsing, FEC coding is applied to the data stream binary input120 by a common FEC encoder 142. In example embodiments, the data streamis segmented into source words that are respectively FEC encoded intorespective code words C1 to CN. The coding rate (e.g., ½, ⅔, ¾, ⅚) thatis applied at encoder 142 is determined by a base MCS selected for allthe RUs. A parser 144 then parses the codewords into N parallel streams,each of which corresponds to a respective RU 1 to RU N. In an exampleembodiment, at least two of the code word streams (e.g. C(i) and C(j))include data that is intended for the same receiving STA 102. Each ofthe code word streams is then modulated at a respective modulator 126(1)to 126(N) and mapped onto a respective set of subcarriers correspondingto a respective RU (e.g., RU 1 to RU N). The modulation type applied ateach of the respective modulators 126(1) to 126(N) is determined by adifferential MCS (relative to the base MCS) selected based on the linkconditions for the corresponding RU 1 to RU N.

Accordingly, in the example of FIG. 7, the code rate assigned for eachRU in multi-RU for a STA is the same due to the use of a single encoder.However, the modulation type for each RU can be different, resulting ina possible use of different MCS for each RU. This embodiment mayoptimize the overall multi-RU performance by optimizing the performanceof each RU based on the common encoding for multiple RUs and thecorresponding individual modulation type. The embodiment of FIG. 7enables a simplified implementation that can be achieved by using onlysingle one encoder combined with variable modulation type to achievepossible different MCSs for each RU in multi-RU for a STA.

At a receiving STA, source words can be recovered by applying a processthat is largely the inverse of that done at a receiving STA. Forexample, a receiving STA 102 can demodulate and decode the PHY header ofa received PPDU to determine what RUs have been assigned to that STA 102and the MCS applied to the RUs. The STA 102 can then demodulate thesignals on the subcarrier sets belonging to the multiple RUs assigned tothat STA 102 based on the modulation type indicated in the recovered MCSinformation. The demodulated RU signals can then be decoded to recoverthe source words based on the coding rate indicated in the recovered MCSinformation. FIG. 8 illustrates selected components of a receiver 146that may be used to recover data from the data portion of a PPDUtransmitted by transmitter such as transmitter 118 and FIG. 9illustrates selected components of a receiver 148 that may be used torecover data from the data portion of a PPDU transmitted by transmittersuch as transmitter 140.

FIG. 10 illustrates an example processing system 150, which may be usedto implement methods and systems described herein, such as the STA 102or the AP-STA 104. Other processing systems suitable for implementingthe methods and systems described in the present disclosure may be used,which may include components different from those discussed below.Although FIG. 8 shows a single instance of each component, there may bemultiple instances of each component in the processing system 150.

The processing system 150 may include one or more processing devices152, such as a processor, a microprocessor, an application-specificintegrated circuit (ASIC), a field-programmable gate array (FPGA), adedicated logic circuitry, or combinations thereof. The processingsystem 150 may also include one or more input/output (I/O) interfaces154, which may enable interfacing with one or more appropriate inputdevices and/or output devices (not shown). One or more of the inputdevices and/or output devices may be included as a component of theprocessing system 150 or may be external to the processing system 150.The processing system 150 may include one or more network interfaces 158for wired or wireless communication with a network. In exampleembodiments, network interfaces 158 include one or more wirelessinterfaces such as transmitters 118 or 140 and receiver 146 or 148 thatenable communications in a WLAN such as network 100. The networkinterface(s) 158 may include interfaces for wired links (e.g., Ethernetcable) and/or wireless links (e.g., one or more radio frequency links)for intra-network and/or inter-network communications. The networkinterface(s) 158 may provide wireless communication via one or moretransmitters or transmitting antennas, one or more receivers orreceiving antennas, and various signal processing hardware and software,for example. In this regard, some network interface(s) 158 may includerespective processing systems that are similar to processing system 150.In this example, a single antenna 160 is shown, which may serve as bothtransmitting and receiving antenna. However, in other examples there maybe separate antennas for transmitting and receiving. The networkinterface(s) 158 may be configured for sending and receiving data to thebackhaul network 110 or to other STAs, user devices, access points,reception points, transmission points, network nodes, gateways or relays(not shown) in the network 100.

The processing system 150 may also include one or more storage units170, which may include a mass storage unit such as a solid state drive,a hard disk drive, a magnetic disk drive and/or an optical disk drive.The processing system 150 may include one or more memories 172, whichmay include a volatile or non-volatile memory (e.g., a flash memory, arandom access memory (RAM), and/or a read-only memory (ROM)). Thenon-transitory memory(ies) 172 may store instructions for execution bythe processing device(s) 152, such as to carry out the presentdisclosure. The memory(ies) 172 may include other software instructions,such as for implementing an operating system and otherapplications/functions. In some examples, one or more data sets and/ormodule(s) may be provided by an external memory (e.g., an external drivein wired or wireless communication with the processing system 150) ormay be provided by a transitory or non-transitory computer-readablemedium. Examples of non-transitory computer readable media include aRAM, a ROM, an erasable programmable ROM (EPROM), an electricallyerasable programmable ROM (EEPROM), a flash memory, a CD-ROM, or otherportable memory storage.

There may be a bus 192 providing communication among components of theprocessing system 150, including the processing device(s) 152, I/Ointerface(s) 154, network interface(s) 158, storage unit(s) 170,memory(ies) 172. The bus 192 may be any suitable bus architectureincluding, for example, a memory bus, a peripheral bus or a video bus.

The present disclosure provides certain example algorithms andcalculations for implementing examples of the disclosed methods andsystems. However, the present disclosure is not bound by any particularalgorithm or calculation. Although the present disclosure describesmethods and processes with steps in a certain order, one or more stepsof the methods and processes may be omitted or altered as appropriate.One or more steps may take place in an order other than that in whichthey are described, as appropriate.

Through the descriptions of the preceding embodiments, the presentinvention may be implemented by using hardware only, or by usingsoftware and a necessary universal hardware platform, or by acombination of hardware and software. Based on such understandings, thetechnical solution of the present invention may be embodied in the formof a software product. The software product may be stored in anon-volatile or non-transitory storage medium, which can be a compactdisk read-only memory (CD-ROM), USB flash drive, or a hard disk. Thesoftware product includes a number of instructions that enable acomputer device (personal computer, server, or network device) toexecute the methods provided in the embodiments of the presentinvention.

Although the present invention and its advantages have been described indetail, it should be understood that various changes, substitutions andalterations can be made herein without departing from the invention asdefined by the appended claims.

Moreover, the scope of the present application is not intended to belimited to the particular embodiments of the process, machine,manufacture, composition of matter, means, methods and steps describedin the specification. As one of ordinary skill in the art will readilyappreciate from the disclosure of the present invention, processes,machines, manufacture, compositions of matter, means, methods, or steps,presently existing or later to be developed, that perform substantiallythe same function or achieve substantially the same result as thecorresponding embodiments described herein may be utilized according tothe present invention. Accordingly, the appended claims are intended toinclude within their scope such processes, machines, manufacture,compositions of matter, means, methods, or steps.

1. A method of transmitting data in an Orthogonal Frequency-DivisionMultiple Access (OFDMA) wireless local area network (WLAN), comprising:parsing input data for transmission for a receiving station into a firstdata stream and a second data stream; modulating, using a firstmodulation type, data included in the first data stream and mapping themodulated data onto a first set of subcarriers associated with a firstresource unit; modulating, using a second modulation type, data includedin the second data stream and mapping the modulated data onto a secondset of subcarriers associated with a second resource unit; andtransmitting, in the WLAN, an orthogonal frequency division multiplexing(OFDM) symbol including the data modulated onto the first set ofsubcarriers and the data modulated onto the second set of subcarriers.2. The method of claim 1 wherein the first set of subcarriers isseparated in frequency from the second set of subcarriers by a pluralityof intervening subcarriers.
 3. The method of claim 1 comprising, priorto modulating using the first modulation type and modulating using thesecond modulation type: receiving a data unit transmitted in the WLAN,selecting the first modulation type and the second modulation type basedon information included in the received data unit.
 4. The method ofclaim 1 comprising, prior to parsing the input data, encoding the dataaccording to a first code rate.
 5. The method of claim 4 comprising:prior to modulating using the first modulation type, encoding the dataincluded in the first data stream based on a first code rate; and priorto modulating using the second modulation type, encoding the dataincluded in the second data stream based on a second code rate.
 6. Themethod of claim 5 comprising: receiving a data unit transmitted in theWLAN; selecting the first modulation type and the first code rate basedon information included in the received data unit; and selecting thesecond modulation type and second code rate based on informationincluded in the received data unit.
 7. The method of claim 6 wherein thefirst modulation type and the second modulation type are each selectedfrom a group of modulation types that includes: binary phase shiftkeying (BPSK) modulation, quadrature phase shift keying (QPSK)modulation; 16-quadrature amplitude modulation (QAM); 64-QAM; 256-QAM;1024-QAM; 2048-QAM; and 4096-QAM.
 8. The method of claim 6 wherein thereceived data unit includes information indicating the first modulationtype, the first code rate, the second modulation type and the secondcode rate in a preamble header of the data unit.
 9. The method of claim1 wherein the OFDM symbol is transmitted as part of a physical payloadof a data unit.
 10. A station for transmitting data in an OrthogonalFrequency-Division Multiple Access (OFDMA) wireless local area network(WLAN), comprising: a network interface configured to send and receivesignals in the WLAN; a processing device coupled to the networkinterface; a non-transitory storage coupled to the processing device andstoring thereon instructions that, when executed by the processingdevice, configure the station to: parse input data for a receivingstation into a first data stream and a second data stream; modulate,using a first modulation type, data included in the first data streamand map the modulated data onto a first set of subcarriers associatedwith a first resource unit; modulate, using a second modulation type,data included in the second data stream and map the modulated data ontoa second set of subcarriers associated with a second resource unit; andtransmit, in the WLAN, an orthogonal frequency division multiplexing(OFDM) symbol including the data modulated onto the first set ofsubcarriers and the data modulated onto the second set of subcarriers.11. The station of claim 10 wherein the first set of subcarriers isseparated in frequency from the second set of subcarriers by a pluralityof intervening subcarriers.
 12. The station of claim 10 wherein, whenexecuted by the processing device, the instructions configure thestation to: receive a data unit transmitted in the WLAN, select thefirst modulation type and the second modulation type based oninformation included in the received data unit.
 13. The station of claim10 wherein, when executed by the processing device, the instructionsconfigure the station to, prior to parsing the input data, encode thedata according to a first code rate.
 14. The station of claim 10wherein, when executed by the processing device, the instructionsconfigure the station to: select, a first code rate for the firstresource unit and a second code rate for the second resource unit; priorto modulating using the first modulation type, encode the data includedin the first data stream based on the first code rate; and prior tomodulating using the second modulation type, encode the data included inthe second data stream based on the second code rate.
 15. The station ofclaim 14 wherein, when executed by the processing device, theinstructions configure the station to: receive a data unit transmittedin the WLAN; select the first modulation type and the first code ratebased on information included in the received data unit; and select thesecond modulation type and second code rate based on informationincluded in the received data unit.
 16. The station of claim 15 whereinthe first modulation type and the second modulation type are eachselected from a group of modulation types that includes: binary phaseshift keying (BPSK) modulation, quadrature phase shift keying (QPSK)modulation; 16-quadrature amplitude modulation (QAM); 64-QAM; 256-QAM;1024-QAM; 2048-QAM; and 4096-QAM, and the OFDM symbol is transmitted aspart of a data unit that includes information indicating the firstmodulation type, the first code rate, the second modulation type and thesecond code rate in a preamble header of the data unit.
 17. The stationof claim 16 wherein the received data unit comprises a header thatincludes, individually for each of the first and second resource unit,information identifying the first set of subcarriers, the firstmodulation type, the second set of subcarriers and the second modulationtype, and the header includes individual subfields for informationidentifying the first modulation type and the second modulation type.18. The station of claim 17 wherein the header further comprises acommon modulation type field indicating a base modulation type, theindividual subfields each indicating a respective difference relative tothe base modulation type, the length of each individual subfield being 3bits or fewer.
 19. A method comprising: receiving, at a receivingstation, a data unit transmitted in wireless local area network (WLAN),the data unit comprising a physical payload that includes an OrthogonalFrequency-Division Multiplexing (OFDM) symbol that has been transmittedin a plurality of resource units used for data modulated according to arespective modulation type, wherein the resource units include a firstand second resource unit assigned to the receiving station and furtherresource units assigned to one or more further receiving stations, thedata unit comprising a header that includes, for each of the first andsecond resource units, information identifying the respective modulationtypes used to modulate the data transmitted in the first and secondresource units, respectively.
 20. The method of claim 19 comprising:demodulating and decoding the header of the received data unit todetermine respective subcarrier sets associated with the first andsecond resource units assigned to the receiving station and therespective modulation types used to modulate the data transmitted in thefirst and second resource units; and demodulating signals on thesubcarrier sets associated with the first and second resource unitsbased on the determined modulation types.
 21. The method of claim 20wherein demodulating and decoding the header of the received data unitalso determines respective coding rates used to encode the datatransmitted in the first and second resource units, the methodcomprising decoding the demodulated signals corresponding to the firstand second resource units based on the determined respective codingrates and combining the decoded and demodulated signals to recovertransmitted source words.
 22. The method of claim 20 whereindemodulating and decoding the header of the received data unit alsodetermines a coding rate used to encode the data transmitted in thefirst and second resource units, the method comprising combining thedemodulated signals and decoding the combined, demodulated signals basedon the determined coding rate and to recover transmitted source words.